1. Field of Invention
The present invention relates to the field of digital systems and is more particularly concerned with the detection of the time difference between transitions in two wave forms.
2. Description of Prior Art
In dealing with digital systems, it is often desirable to investigate wave form transitions from a first level to a second level. Areas of interest in considering transitions occurring on two separate wave forms are: which of two wave forms undergoes a transition first; time between transitions on two separate wave forms; and coincidence, in time, of transitions.
Such investigations in the past have been approached in various ways. One of the most common ways to investigate wave form transitions is with the use of the oscilloscope. This normally requires either a dual trace oscilloscope with an accurate time base, or a single trace oscilloscope with the ability to trigger the sweep from one of the wave forms under study. However, in dealing with very short time intervals, a very wide band or sampling oscilloscope is required. Such instruments are complex and consequently rather expensive.
Another approach to investigating the relative time between transitions on two separate wave forms is to use an event counter, a clock source, and gating means controlled by the wave forms under investigation. However, as the intervals of time between wave form transitions approach the sub-nanosecond range, high-speed, complex and expensive equipment is again required.